Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to printing machines, and more
particularly to inker systems for printing machines, and especially
to lnker systems which apply printing ink to an ink roller which
has a textured surface, such as an anilox roller, which has tiny
depressions or cell~. Inkers suitable for use with anilox rollers
can be constructed in the form of chambered doctor blade inking
systems, and the present invention relates to such inking systems
which are 80 arranged that the cells or receptors of the inking
roller will not be clogged by material rubbed off from the inker
lo system.
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Back~round. The referenced applications
U.S. Serial 07/403,754, ~iled Sept. 6, lsa9, John;
U.S. Serial 07/403,760, filed Sept. 6, 1989, Elock et al7
U.S. Serial 07/403,620, flled Sept. 6, 1989, Bock et al, described
chambered doctor blade units. The chambered doctor blade system
may include housing structure of, in cross section, generally U
shape, and two slde walls. At least one doctor blade, which can
flex in the direction towards the side walls, is engageable towards
an anilox roller.
German Patent disclosure documents DE OS 37 04 433
illustrates a chambered doctor blade unit which has sealing bars
laterally defining the unit. The sealing bars are elastically
biased against the anilox roller and, additionally, can be engaged
against the side edges; of the doctor blade.
It has been found that such a system has a disadvantage
namely that, in the course of operation, wear tracks will form.
InX striping may occur along these wear strips or tracks on the
anilox roller which, in continuous operation, may become thicker
and thicker, BO that ink can splash off therefrom. Uneven ink
supply may occur upon even slightly excess supply of ink to the
unit.
The arrangement by which a doctor blade unit is clamped
laterally between the sealing ~ars requires very precise
maintenance of the length of the doctor blade which increases the
cost, due to the low tolerances which will be needed.
Laterally fitting the edges of the doctor blade against the
sealing bars with even slight pressure results in andulating
deformation of the doctor blade. Typically, doctor blades are
flexible, and have a thicknes of between 0.2 to 0.3 mm. Upon
lateral pressure against such a thin elongated element, it will
form wavy lines so that, upon engagement of such a wavy line with a
clrcumference of the anilox roller, the anilox roller is not
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uniformly stripped of lnk but, rather, lnk ~trlpes may form
thereon. The arrangement, however, require~ a tight flt, laterally
again~t a doctor blade, a~ well as circum~erentlally agalnst the
anilox roller, to prevent lnk from e~caping.
German Patent disclosure document DE OS 32 41 124 ie a
structure which does not use a doctor blade and, only generally,
shows an ink system. German Patent 26 46 071 likewise iB an inker
which does not use a doctor blade, but, rather, has cooperating
inker rollers or cylinders, which are supplled wlth splashing
plates to prevent splashing of ink off the circumferences of the
roller.
The Invention. It is an ob~ect to improve a chambered doctor
blade unit of this type ln such a ~anner that the lateral
boundaries of the unit, typically the side walls, are 80
constructed that no particles rubbed off therefrom can impact in
the receptors or cells of the anilox roller, and which is simple to
construct.
Briefly, the system is designed for inks having a viscosity
of at least 1 d Pa 8 (deci Pascal second), preferably greater than
40 d Pa 8. Each of the side walls, when the inker i8 in operative
position with respect to an anilox roller, form circumferential
gaps with respect to the anilox roller of between about 0.1 to 3
mm. The at least one doctor blade i8 resiliently pressed against
an upper edge of the side walls, and the side walls are formed with
2s inclined relief surfaces which define wedge-shaped gap6 between the
side walls and the doctor blade, at a location beneath the end of
the doctor blade which faces the anilox roller. Excess ink
deflection shields extend from outside of the side walls towards
the ink trough, positioned ad~acent the edge faces of the doctor
blade, to direct ink dripping off, for example from these gaps,
into an ink trough of the inker system.
The inker system of the present invention is particularly
suitable for use in offset printing machines.
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Drawings:
Fig. 1 is a ~chematic ~ide viow Or an lnXer ln accordance
with the present inventlon, engaged againJt an analog
roller, ~hown only in fragmentary ~orm, and in which
all element~ and ~tructural connections, not
necessary for an understanding of the pre~ent
invention, have been omitted;
Fig. 2 is an exploded view of a side wall o~ the inker;
Fig. 3 i8 a fragmentary front view of the inker shown in Fig.
1;
Fig. 4 i8 a prospective view of the side wall of the inker
opposite the one ~hown in Fig. 2;
Fig. 5 is a schematic representation of ink flow arising in
the inker of the present invention, when in operation.
DETAILED DESCRIPTION :
The inker of the present invention is illustrated in an
example intended for use with an offset printing machine, although
it is not limited thereto. A chambered doctor blade unit 1 (Fig.
1) u6es a U-shaped base body 2, two sidewalls 3, and two doctor
blades 4, 5. The doctor blades 4, 5, are clamped by clamping
strips or rails 6, 7 against upper and lower surfaces of the side
walls 3. Screws 8, shown only schematically, provide for the
clamping force. An ink trough 9 is located beneath the inker, as
well known. Structural elements and components to 6ecure the inker
as well as the ink trough to the frame of a print$ng machine have
been omitted since 6uch structural elements can be of any desired
~orm.
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The referenced applications:
U.S. Serial 07/403,754 ~iled Sept. 6, 1989, JO~N
U.S. Serial 07/403,760, flled Sept. 6, 1989, BOCR et al
U.S. Serial 0~/403,620, filed Sept. 6, 1989, BOCK et al
S also illustrate arrangements to attach such a chambered
doctor blade unit to a printing machine.
Tha chambered doctor blade unit can be engaged against an
anilox roller 10, with the two doctor blades 4, 5 in engagement
therewith. The doctor blade 4 removes excess ink when the anilox
roller rotates in the direction of the arrow a: the doctor blade
5 closes off the chambered unit towards the bottom.
As best seen in Fig~. 2 and 4, the respective side walls 3
have a region 11 of reduced width which faces the anilox roller
10. Preferably, the reduction of width is essentially continuous,
becoming narrower towards the doctor blade 10 and terminating in
the front by a curved narrow surface 12. The surface 12 forms a
gap 13 (Fig. 1) with the anilox roller 10. The size A of the gap
is between about 0.1 and 3 mm. It is not necessary that the width
of this gap is uniform throughout the entire length of the surface
12; rather, the width of the gap may vary within the dimensions
given.
The inner ~ide 14 of the region 11 merges with the inner side
15 of the s~de wall 3. The inner side 14 of the region 11,
however, is inclined by an acute angle ~, as best seen in Fig. 4.
The other side 16 of the region 11 engages with an approximately
ri~ht angle against an inclined end wall 17 of the sidewall 13, so
that the outside 16 is inwardly reces6ed with respect to the outer
wall of the wall 3.
In accordance with the feature of the invention the region 11
i~ formed with an inclined surface 19 at the upper 6ide 20 thereof,
which forms an acute angle a with the upper side 20 of the side
wall 3. The inclination 19, which will occur between the doctor
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blade and the top sur~Ace Or the region 11 will ~or~ a wQdge-shaped
gap 21 ~Fig. 1). The helght of this wedgQ-shaped gap, closest to
the outer end of tha doctor blade 4 i8 at least 0.1 mm. The
inclination permits, and insures, that the doctor blade 4, upon
engagement against the anilox roller 10, can rQslliently slightly
deflect. This, in combination with the clamping by the ~aw 6, 7 of
the doctor blades against the upper and lower surfaces,
respectively, of the sidewalls effectively prevents forming of
undulations.
As best seen in Fig. 3, the doctor blade 4 is clamped by the
clamping strip 6 against the base body 2 as well as against the
upper side surface 20 of each one of the side walls 3. The doctor
blade 4 terminates in the plane of the outer wall 18 of the side
wall 3, thus extends with the end facing the anilox roller 10
beyond the regions or zones 11 towards the outside thereof.
The doctor blade 5 is clamped by the clamping strip or rail 7
against the base body 2 and against the lower surfaces of the side
wall 3 including the region 11. It thus closes off the chambered
doctor blade unit 1 up to the surface 12 and seals the unit.
The arrangement can be used not only for inkers ~n which the
anilox roller operates in the direction of the arrow a , but also
for printing machines in which the direction of rotation of the
anilox roller is reversible. In systems in which the direction is
reversible, it is be6t to 80 arrange both doctor blades that they
are inclined towards each other at the end facing the anilox roller
and to use that one of the doctor blades which i8 negatively
engaged against the anilox roller 2 to strip off excess ink.
An excess ink deflection shield 22 is located against the
surface 18 of the side wall 3 and i8 also ad~acent the lateral
outer side of the doctor blade 4. The ink defection shield extends
at one end at least up to the edge surfaces of the doctor blade and
at the other end until just above the ink trough 9. The shield 22
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i8 connected to the associated slde wall 3 by ~crews 23 ~Fig. 3).
Preferably, the lower end 24 o~ the ~hield 22 1~ angled o~f
inwardly 80 that any inX which drips Or~ along the shleld is
reliably directed into the trough 9. Ink run-or~ chambers are
formed betwen shields 22 and the thinner regions ll Or the side
walls 3.
Bypass borss 25 (Figs. 2, 4) may be located in the region 11
of the side walls. This prevent~ undesired excess hydrodynamic
pressure again6t the doctor blade 4 when the inker is in
operation. Such pressure may cause deformation of the doctox blade
which is posit~vely engaged against the doctor blade lO, which
deformation may then lead to non-uniforming engagement against the
anilox roller lO.
operation
When the machine i stopped, and ink i8 upplied to the inker
system, the dynamic viscosity of which i~ greater than l d Pa s,
and preferably greater than 40 d Pa 8, and the inker is engaged
against the anilox roller lO, ink will first ooze out of the gap 13
as well as from the wedge shaped gap 21. InX may escape through
the space between the shield 22 and ths outside 16 of the region 11
of the side wall 3, to be returned to the ink trough 9. It has
been found that, when the anilox roller lO is stopped, hardly any
wetting of the anilox roller lO with ink will occur in the region
of the overlap of the doctor blade 4 beyond the region ll of the
~ide wall 3.
Upon starting the machine, and rotating the roller lO in the
direction of the arrow a , the surface of the anilox roller lO
will accept ink, which will be carried along circumferentially by
the roller 10. Referring to Fig. 5: ink which is not received in
the receptors or cells of the anilox roller lO is carried along in
the direction of the arrows b, c, d . The speed of the ink as
it i8 carried along, immediately ad~acent the anilox roller lO will
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be highest a~ indicated by th~ number o~ arrow~. Toward~ the
inside of the chambered doctor blade unlt, the clrculatlng speed Or
the ink within the unit drops Or~, compare arrow~ b, c and d. At
the same time, in~ flow parallel to the axis of the doctor blade 10
i8 reduced. ~t already intermediate speeds, this has the result
that no ink will escape through tha gap 13. Slight escape of ink
will occur, however, only through the gap 21 beneath the doctor
blade 4, formed by the inclination 19. Any ink escaping from the
gap 21 will be deflected by the shield 22 to drip back lnto the ink
trough 9. Ink escaping through the gaps 21, one at either ~ide of
the inker, insures that the anilox roller 10 is sufficiently in~ed
so that the outer side 16 of the regions 11 of the side wall can
coincide with the edges of subject matter to be printed. The ink
escaping through the gaps 21 still provides ink to the anilox
roller also in the lateral regions that complete tonal depth for
printing is obtained even in the side regions within measurable
tolerances; beyond this limit, however, the anilox roller will not
be inked.
The unit 1 is not in physical engagement with the anilox
roller, rather is applied towards the anilox roller contact-less.
Consequently, no wear and tear o~ the curved surfaces 12 will
arise, and no filling of cells or receptors in the anilox roller
will result. Resilient ad~ustment elements are not necessary, in
order to compensate for any wear and tear upon phy6ical
engagement.
Varlous changes and modifications may be made within the
scope of the inventive concept.
